One of the most anticipated rematches in UFC history is set for June 23.

Anderson Silva will defend his UFC middleweight title against Chael Sonnen for the second time on that date at Rio de Janeiro's Estádio Olímpico João Havelange. According to UFC president Dana White, the venue will hold approximately 80,000 fans for the event. If so, that would make it the biggest card in UFC history.

However, according to Sonnen, nothing is official just yet.

"My demand has not been met," Sonnen told NBCSports.com when asked for a comment on the rematch. "I've signed nothing."

Sonnen's manager Mike Roberts also confirmed that Sonnen has yet to sign a bout agreement, but it appears as though that is just a formality at this point.

As for what his demand is, Sonnen only said, "it's coming."

Also scheduled to take place at UFC 147 is Wanderlei Silva vs. Vitor Belfort 2, the finals of TUF: Brazil and Fabricio Werdum vs. Mike Russow.

Silva submitted Sonnen in the fifth round of their classic UFC 117 bout in Aug. 2010.

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